1. Field of the Invention
The present invention generally relates to semiconductor manufacturing and fabrication. More specifically, the present invention relates to methods and apparatuses for using a synchrotron as a source in extreme ultraviolet lithography.
2. Related Art
Rapid advances in computing technology have made it possible to perform trillions of computational operations each second on data sets that are sometimes as large as trillions of bytes. These advances can largely be attributed to the dramatic improvements in semiconductor manufacturing technologies which have made it possible to integrate tens of millions of devices onto a single chip.
Conventional photolithography processes are close to reaching their physical limit in terms of the minimum feature size that can be printed. Hence, the semiconductor industry is actively considering various next generation technologies which will enable feature sizes to be miniaturized even further. One of the more promising technologies is extreme ultraviolet lithography (EUVL) which uses approximately 13 nm light (hereinafter referred to as “13 nm” light).
Today's EUVL systems are not ready for mass-scale manufacturing because of serious technological problems with the illumination source, the photoresist, and the mask. The EUVL illumination source has two significant problems: power and reliability. The extreme ultraviolet sources that are being considered for use in EUVL are able to deliver 5-10 mJ/mm2 to a wafer surface, with a slow throughput rate. Specifically, a commonly used source generates EUVL light by shooting a metallic tape or a gas with a laser, which causes a 13 nm pulse to be produced. However, the pulse rate is low and the process is not very clean, which causes this source to have a short lifetime and low power.
The photoresist problem in EUVL is also directly related to the problems with the source. First, most materials absorb 13 nm light, so penetrating deep (˜100 nm) into photoresist is very difficult. Second, EUVL photoresist materials usually have significant contrast and line edge roughness problems, which means that the photoresist material has difficulty in distinguishing between the high and low portions of the optical transmission signal. Unfortunately, if the source has low power, it exacerbates both the contrast and line edge roughness problems.
Mass-scale manufacturing typically requires a throughput of 100 wafers per hour. However, the EUVL sources that the industry is currently considering result in a throughput of 10 wafers per hour, and are estimated to cost between $5 and $10 million per unit. Hence, EUVL systems that use these EUVL sources are most likely not going to be economically viable.